Communicating apparatus

ABSTRACT

A communication apparatus ( 100 ) includes a first antenna (A 1 ) for receiving carriers on which information signals, which are modulated signals, are superimposed; a ground terminal ( 50 ) for causing a reference voltage to be close to zero; a second antenna (A 2 ) (i) that is connected to the ground terminal and (ii) that exhibits an electromagnetically opposite polarity to the first antenna; and a signal processing element ( 10 ) that processes the received information signals.

TECHNICAL FIELD

The present invention relates to a communicating apparatus usingelectromagnetic waves, such as an AM receiver and signal communicationequipment.

BACKGROUND ART

Wireless communication using electromagnetic waves generally includes anAM (Amplitude Modulation) receiving apparatus (a so-called receivingdevice or receiver) and a receiving antenna. The AM receiving apparatusis normally not earthed to the ground, so the reference potential of theAM receiving apparatus always varies with respect to the ground, whichis due to reference terminals, which make the reference potential ofvoltage switching in a switching power supply, an inner circuit providedwith an oscillation circuit, and the AM receiving apparatus, andoperations of a plurality of circuit elements, which are connected tothe reference terminals.

In the wireless communication, if the frequency of a carrier wave onwhich a desired information signal (a so-called modulated signal) issuperimposed is close to or equal to the frequency of the referencepotential variation (the variation in the reference potential), it ishard to receive the desired carrier wave and to perform signalprocessing. This is because the receiving antenna, connected to the AMreceiving apparatus, is connected to the reference potential andoperates on the basis of the reference potential, so the receivingantenna receives not only the carrier wave on which the desiredmodulated signal is superimposed but also a noise corresponding to anelectromotive force generated between terminals of the antenna becauseof the variation in the reference potential. If the noise level isgreater than that of the carrier wave on which the desired modulatedsignal is superimposed, the signal level of the desired modulated signalis relatively reduced, which makes it hardly possible or impossible toreceive the carrier wave on which the desired modulated signal issuperimposed and to perform the signal processing on the carrier wave.Even if the noise level is relatively small, a SN ratio (Signal to NoiseRatio) is significantly reduced, which likely causes such acommunication failure as an audience hardly listens to the desiredmodulated signal.

For the generation of the noise caused by the variation in the referencepotential and a communication jamming caused by the generated noise, thefollowing three main types of countermeasures have been suggested. Thefirst type is to take countermeasures in control methods and partaddition, to thereby reduce the noise caused by the reference potentialvariation, with respect to a circuit operation which causes thevariation in the reference potential. The second type is to takestructural countermeasures, such as an electromagnetic shield, tothereby avoid the jamming by the noise caused by the reference potentialvariation. The third type is to earth the reference potential of the AMreceiving apparatus to the ground, to thereby stabilize the referencepotential.

The first and second countermeasures do not provide a fundamentalsolution unless the circuit operation, which causes the variation in thereference potential, such as an oscillating operation and voltageswitching, is completely stopped or the reference potential of thereceiving apparatus is completely isolated from the noise source.Various specific countermeasures were worked in the past; however, thereis a limit on effectiveness even if the countermeasures are taken.Moreover, the countermeasures cause an increase in the number of partsand complicated control, which are factors in increased cost.

The third countermeasure sufficiently provides a jamming preventioneffect (so-called an effect in which an influence by the noise can besufficiently prevented) if the reference potential of the receiver canbe earthed or grounded to a stable potential. In reality, however,depending on an environment and place in which the communicatingapparatus is used, the physically and electrically stable groundingenvironment is most likely not ensured. Even if the groundingenvironment can be ensured, it is extremely disadvantageous (ordemeritorious) to have a user perform a grounding operation, in terms ofthe user's convenience, i.e. usability.

A patent document 1 or the like discloses a method of controlling aswitching frequency not to influence the frequency of the carrier waveto be received, in accordance with a reception interference occurring ifthe switching frequency is close to or equal to the reception frequencyin the method of controlling the switching power supply, which is one ofthe causes for the variation in the reference potential, which causesthe reception interference and the reduction in the SN ratio.

-   Patent document 1: Japanese Patent Application Laid Open No.    2005-237044

DISCLOSURE OF INVENTION Subject to be Solved by the Invention

In the aforementioned patent document 1 or the like, however, since thespecial control method for preventing the generation of the noise,endogenously-caused by the switching power supply, complicates thedesign of the power supply, it is sometimes hard to change the designfrom that of the existing communication apparatus in terms of techniquesor cost. Even if the generation of the noise from the switching powersupply owned by the AM receiver is significantly prevented thanks to theaforementioned patent document 1 or the like, there still remains aninfluences of oscillation circuits provided inside or outside variousICs (Integrated Circuits) such as a micro computer, a DSP (DigitalProcessing Unit), and a switching circuit like a digital amplifier.

Moreover, this technology cannot deal with an influence of anotherelectronic equipment which is connected to the receiver in the referencepotential. Furthermore, in general, the oscillation frequency of theswitching power supply has a relatively large time fluctuation (jitter),the frequency width of a switching frequency spectrum cannot be ignoredwith respect to the reception frequency step of the receiver in mostcases. Therefore, even if a predetermined frequency is controlled, it ishard to completely prevent the jamming or interference because thespectrum of the switching frequency cannot be fully separated from thereception frequency of the receiver. In substantially the same manner,it is technically hard that the one countermeasure for theaforementioned power supply is an effective countermeasure to preventthe generation of the noise, with respect to the circuit structure of adifferent type from the power supply of the oscillation circuit or thelike.

In view of the aforementioned problems, it is therefore an object of thepresent invention to provide a communicating apparatus which useselectromagnetic waves, which can prevent the reception interference bythe noise, and which can improve the SN ratio.

Means for Solving the Subject

The above object of the present invention can be achieved by acommunicating apparatus according to claim 1, provided with: a firstantenna for receiving a carrier wave on which an information signal,which is a modulated signal, is superimposed; a ground terminal forbringing a reference potential close to zero; a second antenna, (i)which is connected to the ground terminal and (ii) which has anelectromagnetically reverse polarity of the first antenna; and a signalprocessing device for performing signal processing on the receivedinformation signal.

These operation and other advantages of the present invention willbecome more apparent from the embodiments explained below.

Best Mode for Carrying Out the Invention

Hereinafter, as the best mode for carrying out the present invention, anexplanation will be given on a communicating apparatus in an embodimentof the present invention.

(Embodiment of Communicating Apparatus)

An embodiment of the communicating apparatus of the present invention isa communicating apparatus provided with: a first antenna for receiving acarrier wave on which an information signal, which is a modulatedsignal, is superimposed; a ground terminal for bringing a referencepotential close to zero; a second antenna, (i) which is connected to theground terminal and (ii) which has an electromagnetically reversepolarity of the first antenna; and a signal processing device forperforming signal processing on the received information signal.

According to the embodiment of the communicating apparatus of thepresent invention, the carrier wave on which the modulated signal issuperimposed is received by the first antenna. Then, the signalprocessing, such as synchronizing, demodulating, and amplifying, isperformed on the received carrier wave by the signal processing device.The “antenna” of the present invention denotes an aerial for receivingthe electromagnetic waves used for wireless communication. As onespecific example of the antenna, a loop antenna used for an AM receiverand a bar antenna (or linear antenna) used for portable equipment or thelike can be listed.

In particular, according to the present invention, the second antenna,which has the electromagnetically reverse polarity of the first antenna,is connected to the ground terminal for bringing the reference potentialclose to zero.

If there is no second antenna, a variation in the reference potentialcauses a noise corresponding to an electromotive force generated in animpedance between the terminals of the first antenna. This interfereswith the signal processing of the carrier wave and significantly reducesa SN ratio (Signal to Noise Ratio). In contrast, according to theembodiment, the second antenna, which has the electromagneticallyreverse polarity of the first antenna, can generate a positive magneticfield for cancelling a negative magnetic field which is generated by thenoise corresponding to the electromotive force generated in theimpedance between the terminals of the first antenna. Therefore, areverse electromotive force is generated with respect to theelectromotive force generated in the impedance between the terminals ofthe first antenna. Therefore, the variation in the reference potentialcan be canceled, so that it is possible to almost or completely cancelthe noise generated by the variation in the reference potential.

Consequently, it is possible to almost or completely cancel the noisegenerated by the variation in the reference potential, to prevent thereception inference, and to dramatically improve the SN ratio, in thecommunicating apparatus.

In particular, according to the embodiment, it is possible to specifythe type, place, or characteristic of the cause for the variation in thereference potential in the communicating apparatus, and it is possibleto almost or completely eliminate the need to individually provide thecountermeasure.

If in focusing on (i) a circuit method and a circuit structure withinthe communicating apparatus or (ii) the structure, type, and property ofa power supply for supplying an electric power to the signal processingapparatus, it is hard to change the design from that of the existingcommunicating apparatus in terms of techniques or cost. Because variousmethods which is for preventing the generation of the noise,endogenously-caused by (i) the circuit method and circuit structure or(ii) the power supply, complicate the design of (i) the circuit methodand circuit structure or (ii) the power supply, which is based on aspecial control method. Even if the generation of the noise from theswitching power supply owned by the AM receiver is significantlyprevented thanks to the aforementioned patent document 1 or the like,there still remains an influences of oscillation circuits providedinside or outside various ICs (Integrated Circuits) such as a microcomputer, a DSP (Digital Processing Unit), and a switching circuit likea digital amplifier. In substantially the same manner, it is technicallyhard that the countermeasure for the aforementioned power supply is aneffective countermeasure to prevent the generation of the noise, withrespect to the circuit structure of a different type from the powersupply of the oscillation circuit or the like. Moreover, even if thegeneration of the noise is prevented in one AM receiver thanks to theaforementioned patent document 1 or the like, it is technically hard toprevent the generation of the noise in another electronic equipment thatis electrically connected to the one AM receiver.

In contrast, in the embodiment, the variation in the reference potentialcan be cancelled on the basis of the second antenna which has theelectromagnetically reverse polarity of the first antenna, so that it ispossible to almost or completely cancel the noise caused by thevariation in the reference potential, to prevent the receptioninterference, and to dramatically improve the SN ratio, radically andappropriately without depending on (i) the circuit method and circuitstructure within the communicating apparatus or (ii) the structure,type, and property of the power supply for supplying an electric powerto the signal processing apparatus. In addition, according to theembodiment, it is possible to almost or completely cancel the noise inone communicating apparatus, and it is also possible to almost orcompletely cancel the noise in another electronic equipment that iselectrically connected to the one communicating apparatus.

In addition, according to the embodiment, it is only necessary to addthe second antenna to the existing communicating apparatus, so that itis possible to dramatically improve the SN ration, simply andinexpensively. Moreover, a user can omit the procedure of grounding thecommunicating apparatus, which is normally preferred, so that it ispossible to significantly improve the user's convenience.

In one aspect of the embodiment of the communicating apparatus of thepresent invention, (i) one end of the second antenna is connected to theground terminal and (ii) the other end of the second antenna is open oris terminated in an impedance of a predetermined amount substantiallyequivalent to the case of being open.

According to this aspect, the other terminal of the second antenna (i,e.a hot terminal) is open or is terminated in an impedance of apredetermined amount substantially equivalent to the case of being open.Here, the predetermined amount in the present invention denotes anamount which is sufficiently large and which can realize the impedancesubstantially equivalent to the case of being open. The predeterminedamount may be defined, individually and specifically, on theexperimental, theoretical, experiential, and simulation basis. Thus, thesecond antenna hardly functions as an antenna aiming for the reception,as in the first antenna, with respect to the carrier wave on which thedesired modulated signal is superimposed, in other words, theelectromagnetic wave whose reception is desired. As a result, it ispossible to cancel the noise while maintaining the high signal level ofthe desired modulated signal because there is little or no influence onthe reception sensitivity and reception property of the first antenna.

In another aspect of the embodiment of the communicating apparatus ofthe present invention, the first antenna and the second antenna areelectromagnetically integrally connected.

According to this aspect, it is possible to cancel the noise, moreappropriately and highly accurately; on the basis of the first antennaand the second antenna, which are electromagnetically integrallyconnected.

In another aspect of the embodiment of the communicating apparatus ofthe present invention, the ground terminal is connected to (i) a firstreference terminal, which is the reference potential of the signalprocessing device, and (ii) all or a part of circuit elements connectedto the first reference terminal.

According to this aspect, the ground terminal of the communicatingapparatus is connected to (i) the first reference terminal, which makesthe reference potential of the signal processing device, and (ii) theall or a part of circuit elements connected to the first referenceterminal, so that it is possible to specify the type, place, orcharacteristic of the cause for the variation in the reference potentialin the power supply, oscillation circuit, or case, and it is possible toalmost or completely eliminate the need to individually provide thecountermeasure.

If in focusing on (i) the circuit method and circuit structure withinthe communicating apparatus or (ii) the structure, type, and property ofthe power supply for supplying an electric power to the signalprocessing apparatus, it is hard to change the design from that of theexisting communicating apparatus in terms of techniques or cost. Becausethe various methods which is for preventing the generation of the noise,endogenously-caused by (i) the circuit method and circuit structure or(ii) the power supply, complicate the design of (i) the circuit methodand circuit structure or (ii) the power supply, which is based on aspecial control method. Even if the generation of the noise from theswitching power supply owned by the AM receiver is significantlyprevented thanks to the aforementioned patent document 1 or the like,there still remains an influences of oscillation circuits providedinside or outside various ICs (Integrated. Circuits) such as a microcomputer, a DSP (Digital Processing Unit), and a switching circuit likea digital amplifier. In substantially the same manner, it is technicallyhard that the countermeasure for the aforementioned power supply is aneffective countermeasure to prevent the generation of the noise, withrespect to the circuit structure of a different type from the powersupply of the oscillation circuit or the like. Moreover, even if thegeneration of the noise is prevented in one AM receiver thanks to theaforementioned patent document 1 or the like, it is technically hard toprevent the generation of the noise in another electronic equipment thatis electrically connected to the one AM receiver.

In contrast, in the embodiment, the variation in the reference potentialcan be cancelled on the basis of the second antenna which has theelectromagnetically reverse polarity of the first antenna, so that it ispossible to almost or completely cancel the noise caused by thevariation in the reference potential, to prevent the receptioninterference, and to dramatically improve the SN ratio, radically andappropriately without depending on (i) the circuit method and circuitstructure within the communicating apparatus or (ii) the structure,type, and property of the power supply for supplying an electric powerto the signal processing apparatus.

Specifically, the ground terminal may be connected at least one of (ii)a second reference terminal, which makes the reference potential of acase for storing therein the signal processing device; (iii) a thirdreference terminal, which makes the reference potential of a powersupply; and (iv) a fourth reference terminal, which makes the referencepotential of an oscillation circuit provided for the signal processingdevice.

More specifically, various reference terminals can be listed which makethe reference potential of various ICs (Integrated Circuits) such as amicro computer, a DSP (Digital Processing Unit), and a switching circuitlike a digital amplifier, in addition to the signal processing device,such as a reception circuit, and the power supply provided in the case.

The plurality of reference terminals may share the reference potentialand may be stored in the case in one electronic equipment.Alternatively, the plurality of reference terminals may be stored in aplurality of cases in a plurality of electronic equipments, may beelectrically connected over the plurality of cases by a conducting wiresuch as a pin cable, and may make the common reference potential. As aresult, it is possible to almost or completely cancel the noise in onecommunicating apparatus and it is also possible to almost or completelycancel the noise in another electronic equipment that is electricallyconnected to the one communicating apparatus.

In another aspect of the embodiment of the communicating apparatus ofthe present invention, the first antenna and the second antenna are (i)electromagnetically integrally connected and physically integrallyconnected, or (ii) electromagnetically integrally connected but notphysically integrally connected.

According to this aspect, the first antenna and the second antenna arephysically integrally connected, so that they cannot be physicallydifferent two components; namely, the first antenna may apparentlyinclude the second antenna by adding a winding for performingsubstantially the same operations as the second antenna.

As a result, at a stage of designing, it is possible to design theelectromagnetically close connection of the two types of loop antennaswith different electromagnetic properties: the first antenna and thesecond antenna. Thus, it is possible to improve the effect of preventingthe jamming or interference by the noise and to further improve the SNratio. Moreover, a user can use the communicating apparatus with thesame recognition and feelings as those for the conventional loopantenna.

Alternatively, the first antenna and the second antenna can bephysically different two components because they are electromagneticallyintegrally connected but not physically integrally connected. As aresult, it is only necessary to add a designing process and amanufacturing process for the second antenna to the existing designingprocess and manufacturing process, so that it is possible to reduce themanufacturing cost.

These operation and other advantages of the present invention willbecome more apparent from the example explained below.

As explained above, according to the embodiment of the communicatingapparatus of the present invention, it is provided with the firstantenna, the ground terminal, the second antenna, and the signalprocessing device. As a result, it is possible to almost or completelycancel the noise caused by the variation in the reference potential, toprevent the reception interference, and to dramatically improve the SNratio, in the communicating apparatus.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram conceptually showing the basic structureof an AM (Amplitude Modulation) receiving apparatus in an example of thecommunicating apparatus of the present invention.

FIG. 2 is an outside perspective view schematically showing andfeaturing first and second loop antennas of the basic structure of theAM receiving apparatus in the example of the communicating apparatus ofthe present invention.

FIG. 3 is a schematic diagram conceptually showing the basic structureof an AM (Amplitude Modulation) receiving apparatus in a comparisonexample.

FIG. 4 is an outside perspective view schematically showing andfeaturing a first loop antenna of the basic structure of the AMreceiving apparatus in the comparison example.

FIG. 5 are a graph (FIG. 5( a)) quantitatively showing the effect of theexample on the basis of gain limited sensitivity (or maximumsensitivity) and a graph (FIG. 5( b)) quantitatively showing the effectof the example on the basis of noise limited sensitivity (or practicalsensitivity).

FIG. 6 are a graph (FIG. 6( a)) quantitatively showing the effect of theexample on the basis of attenuation and a graph (FIG. 6( b))quantitatively showing the effect of the example on the basis of a SNratio.

FIG. 7 is a table quantitatively showing the effect of the example onthe basis of the attenuation and the SN ratio.

DESCRIPTION OF REFERENCE CODES

-   10 signal processing circuit-   20 oscillation circuit-   30 switching power supply-   100 AM receiving apparatus-   A1 first loop antenna-   A2 second loop antenna

Example

Hereinafter, a preferred example of the communicating apparatus of thepresent invention will be explained with reference to the drawings.

(1) Basic Structure

Firstly, with reference to FIG. 1, an explanation will be given on thebasic structure of the example of the communicating apparatus of thepresent invention. FIG. 1 is a schematic diagram conceptually showingthe basic structure of an AM (Amplitude Modulation) receiving apparatus(or a receiver) in the example of the communicating apparatus of thepresent invention. FIG. 2 is an outside perspective view schematicallyshowing and featuring first and second loop antennas of the basicstructure of the AM receiving apparatus in the example of thecommunicating apparatus of the present invention.

As shown in FIG. 1, an AM receiving apparatus 100 in the example, isprovided with a first loop antenna A1, a second loop antenna A2, asignal processing circuit 10, an oscillation circuit 20, a switchingpower supply 30, and a grounding wire 50. Incidentally, in the example,the loop antenna used for the AM receiver, is used as one specificexample of the “antenna” of the present invention; however, it is alsopossible to use a bar antenna (or a linear antenna), which is used forportable equipment or the like.

In particular, in the example, the grounding wire 50 may be connected toall the circuit elements that are connected to reference terminals,which is the reference potential of the signal processing circuit 10, inaddition to be the reference potential of the electronic elementdescribed above. More specifically, the grounding wire 50 may beconnected to (i) the reference terminal, which is the referencepotential of the power supply; and (ii) the reference terminal, which isthe reference potential of an oscillation circuit provided for thesignal processing circuit 10. More specifically, it is possible to listvarious reference terminals, which is the reference potential in theoscillation circuits provided inside or outside various ICs (IntegratedCircuits) such as a micro computer, a DSP (Digital Processing Unit), anda switching circuit like a digital amplifier, in addition to be thereference potential of the power supply which exists in a case and asignal processing device such as a reception circuit or a receivingcircuit. The plurality of reference terminals may be stored within thecase of one electronic equipment, with the reference potential as acommon reference potential. Alternatively, the plurality of referenceterminals may be stored in respective cases of a plurality of electronicequipments, may be electrically connected over the plurality of cases bya conducting wire such as a pin cable, and may be the common referencepotential. As a result, it is possible to almost or completely cancelthe noise in one communicating apparatus and it is also possible toalmost or completely cancel the noise in another electronic equipmentthat is electrically connected to the one communicating apparatus.

In the first loop antenna A1 and the second loop antenna A2, an element(i.e. a conducting wire, a conductor portion) is made cyclic (orlooped). This type of loop antenna is formed by winding the conductingwire several times with a diameter larger than that of the normal coilused as an electronic part. The operation principle of the loop antennauses that an induced electromotive force is extracted by using a changein a magnetic field within the coil. In this case, the length of theconducting wire of the loop antenna is not directly related to theoperations. Most loop antennas are used as a resonance circuit, with itconnected to a condenser. More specifically, as this representativeproduct, a long distance reception antenna for a medium-wave-band AMradio is commercially available. This is to be synchronized by avariable condenser with a coil in a shape of triangle, quadrangle, orthe like having a diameter of about one meter, and this is to beelectrically connected to the bar antenna built in the radio.Incidentally, the details of the first loop antenna A1 and the secondloop antenna A2 in the example, will be detailed later.

The signal processing circuit 10 is an electronic circuit installed in ageneral AM radio, and the signal processing circuit 10 is provided with,for example, a high-frequency amplifier, a mixer, the aforementionedoscillation circuit 20 (a so-called local oscillator), an intermediatefrequency amplifier, a demodulator, and a low-frequency amplifier. Thesignal processing circuit 10 is connected to the grounding wire 50 andoperates on the basis of the reference potential of the grounding wire50.

The switching power supply 30 is a power supply apparatus which uses aswitching element (e.g. an element that allows one portion of anelectric circuit such as a switching circuit to be turned on or off) forconverting or adjusting an electric power, on an electric powerconverting apparatus which obtains a desired output power from an inputpower. In particular, the switching power supply 30 may be a so-calledswitching regulator. Specifically, the switching power supply 30 may bea DC-to-DC convertor which converts a direct-current power to anotherdirect-current power, or it may be a power supply apparatus providedwith a rectifying apparatus (an AC-to-DC convertor) for converting analternating-current power to a constant direct-current power. Morespecifically, a switching circuit provided for the switching powersupply 30 switches, i.e. turns on and off, a direct-current voltagesmoothed by an electrolytic capacitor, at high frequencies of severalkHz to several MHz. By switching at the high frequencies, it is possibleto reduce an inductance necessary for a trance or a choke coil. Namely,it is possible to reduce the number of turns and core of the trance orthe choke coil, leading to miniaturization.

In the AM receiving apparatus 100, in general, a reference potential V0,i.e. GNB (Ground), has substantially the same potential (i.e. potentiallevel) as one terminal of the first loop antenna A1 (i.e. a coldterminal: refer to a thin line connected to the first loop antenna A1 inFIG. 2) for receiving a carrier wave on which a modulated signal issuperimposed. Thus, a variation in the reference potential V0 of thegrounding wire 50 causes an electromotive force in the impedance of thefirst loop antenna A1. Therefore, a voltage is generated between twoterminals (i.e. antennal terminals) of the first loop antenna Al.Incidentally, the voltage generated between the two terminals because ofthe reference potential variation, is denoted by “v(t)” in which time“t” is a variable. The voltage “v(t)” is a noise voltage (i.e. aninterference or disturbance voltage) which interferes with appropriatesignal processing. The voltage “v(t)” reduces the relative signal levelof the desired modulated signal superimposed on the carrier wave andsignificantly reduces a SN ratio (Signal to Noise Ratio). Incidentally,a magnetic field “B(t)”, uniquely determined from the voltage v(t), isgenerated from the first loop antenna A1. The magnetic field “B(t)”approaches zero, when the voltage v(t) approaches zero.

In particular, the AM receiving apparatus 100 in the example, isprovided with the second loop antenna A2, as shown in FIG. 1 and FIG. 2.One terminal of the second loop antenna A2 (i.e. a cold terminal: referto a thin line connected to the second loop antenna A2 in FIG. 2) isconnected to the reference potential V0 of the grounding wire 50 in theAM receiving apparatus 100. And the other terminal (i.e. a hot terminal)is open to the air as an open terminal (refer to a thick line connectedto the second loop antenna A2 in FIG. 2), or is terminated in animpedance of a predetermined amount substantially equivalent to the caseof being open. Here, the predetermined amount in the example, denotes anamount that is large enough and that can realize the impedancesubstantially equivalent to the case of being open. The predeterminedamount may be defined, individually and specifically, on an experiment,theoretic, experiential, or simulation basis.

As described above, any one of the antenna input terminals owned by theAM receiving apparatus, is connected to the reference potential. At thesame time, the second loop antenna A2 has the electromagneticallyreverse polarity of the first loop antenna A1. Therefore, the secondloop antenna A2 can function as an antenna for cancelling the noisecaused by the variation in the reference potential. Specifically, awinding direction in the conducting wire of the second loop antenna A2,is preferably opposite to a winding direction of the first loop antennaA1. Here, the “hot terminal” in the example, denotes a terminalcorresponding to a position at which the loop antenna starts winding.Moreover, the “cold terminal” in the example, denotes a terminalcorresponding to a position at which the loop antenna ends winding.Incidentally, the conducing wire connected to the “hot terminal” in FIG.2, is shown in the thick line, and the conducting wire connected to the“cold terminal” in FIG. 2, is shown in the thin line.

In addition, the first loop antenna Al and the second loop antenna A2are preferably connected closely and integrally as much aselectromagnetically possible (refer to a circle which indicates the“electromagnetically close connection” in FIG. 2). Specifically, thefirst loop antenna Al and the second loop antenna A2 may be (i)electromagnetically integrally connected and physically integrallyconnected. The first antenna and the second antenna are physicallyintegrally connected, so that they cannot be physically different twocomponents. Namely, the first antenna may apparently include the secondantenna by adding a winding for performing substantially the sameoperations as the second antenna.

As a result, at a stage of designing, it is possible to design theelectromagnetically close connection of the two types of loop antennaswith different electromagnetic properties: the first antenna and thesecond antenna. Thus, it is possible to improve the effect of preventingthe jamming or interference by the noise and to further improve the SNratio. Moreover, a user can use the communicating apparatus with thesame recognition and feelings as those for the conventional loopantenna.

Alternatively, the first antenna and the second antenna may be (ii)electromagnetically integrally connected but not physically integrallyconnected. Therefore, they can be physically different two components.As a result, it is only necessary to add a designing process and amanufacturing process for the second antenna to the existing designingprocess and manufacturing process, so that it is possible to reduce themanufacturing cost. As described above, the magnetic field “B(t)”,caused by the potential variation in the reference potential V0 of thegrounding wire 50, is generated from the first loop antenna A1. On theother hand, from the second loop antenna A2, a reverse magnetic field“−B(t)” is generated. Thus, the magnetic field “B(t)” generated in thefirst loop antenna Al and the magnetic field “−B(t)” generated in thesecond loop antenna A2 cancel each other. Therefore, simultaneously withthe magnetic field “B(t)” generated in the first loop antenna A1approaching zero, the voltage “v(t)” generated between the two terminalsof the first loop antenna Al approaches zero.

As a result, by almost or completely cancelling the noise caused by thevariation in the reference potential V0 in the AM receiving apparatus100, it is possible to prevent the reception interference and it is alsopossible to dramatically improve the SN ratio.

In particular, the other terminal (i.e. hot terminal) of the second loopantenna A2 is open or is terminated in the impedance of thepredetermined amount substantially equivalent to the case of being open.Thus, the second loop antenna A2 does not function as an antenna aimingfor the reception, as in the first loop antenna A1, because theimpedance is substantially infinite, with respect to the carrier wave onwhich the desired modulated signal is superimposed, in other words, withrespect to the electromagnetic wave whose reception is desired.

(2) First Study on Operation and Effect in Example

Next with reference to the aforementioned FIG. 1 and FIG. 2 as occasiondemands in addition to FIG. 3 and FIG. 4, a first study is given to theoperation and effect in the example. FIG. 3 is a schematic diagramconceptually showing the basic structure of an AM (Amplitude Modulation)receiving apparatus (or a receiver) in a comparison example. FIG. 4 isan outside perspective view schematically showing and featuring a firstloop antenna of the basic structure of the AM receiving apparatus in thecomparison example.

As shown in FIG. 3 and FIG. 4, in the AM receiving apparatus 100 in thecomparison example, the reference potential V0, i.e. GND (Ground), hassubstantially the same potential (i.e. potential level) as one terminalof the first loop antenna A1 (i.e. a cold terminal: refer to a thin lineconnected to the first loop antenna A1 in FIG. 4) for receiving aninformation signal. Thus, the variation in the reference potential V0 ofthe grounding wire 50 causes an electromotive force in the impedance ofthe first loop antenna A1. Therefore, a voltage is generated between twoterminals (i.e. antennal terminals) of the first loop antenna A1. Thevoltage “v(t)” is a noise voltage (i.e. an interference or disturbancesignal) which interferes with appropriate signal processing. The voltage“v(t)” reduces the relative signal level of the desired modulated signalsuperimposed on the carrier wave and significantly reduces the SN ratio.

In contrast, the AM receiving apparatus 100 in the example, as shown inthe aforementioned FIG. 1 and FIG. 2, is provided with the second loopantenna A2. One terminal of the second loop antenna A2 (i.e. a coldterminal) is connected to the reference potential V0 of the groundingwire 50 in the AM receiving apparatus 100. And the other terminal (i.e.a hot terminal) is open to the air as an open terminal or is terminatedin an impedance of a predetermined amount substantially equivalent tothe case of being open. At the same time, the second loop antenna A2 hasthe electromagnetically reverse polarity of the first loop antenna A1.Therefore, the second loop antenna A2 can function as an antenna forcancelling the noise caused by the variation in the reference potential.

As a result, it is possible to almost or completely cancel the noisecaused by the variation in the reference potential V0, to prevent thereception interference, and to dramatically improve the SN ratio, in theAM receiving apparatus 100.

In addition, according to the example, it is possible to specify thetype, place, or characteristic of the cause for the variation in thereference potential in the AM receiving apparatus 100, and it ispossible to almost or completely eliminate the need to individuallyprovide the countermeasure.

If in focusing on (i) the circuit method and circuit structure withinthe AM receiving apparatus 100 or (ii) the structure, type, and propertyof the switching power supply 30 for supplying an electric power to thesignal processing apparatus, it is hard to change the design from thatof the existing AM receiving apparatus 100 in terms of techniques orcost. Because the various methods, which is for preventing thegeneration of the noise, endogenously-caused by (i) the circuit methodand circuit structure or (ii) the switching power supply 30 complicatethe design of (i) the circuit method and circuit structure or (ii) theswitching power supply 30, which is based on a special control method.In substantially the same manner, it is technically hard that the onecountermeasure for the aforementioned switching power supply 30 is aneffective countermeasure to prevent the generation of the noise, withrespect to the circuit structure of a different type from the powersupply of the oscillation circuit or the like.

In contrast, in the example, the variation in the reference potentialcan be cancelled on the basis of the second loop antenna A2 which hasthe electromagnetically reverse polarity of the first loop antenna A1,so that it is possible to almost or completely cancel the noise causedby the variation in the reference potential And it is possible toprevent the reception interference, and it is possible to dramaticallyimprove the SN ratio, radically and appropriately, without depending on(i) the circuit method and circuit structure within the AM receivingapparatus 100 or (ii) the structure, type, and property of the switchingpower supply 30 for supplying an electric power to the signal processingapparatus.

In addition, according to the example, it is only necessary to add thesecond loop antenna A2 to the existing AM receiving apparatus 100, sothat it is possible to prevent the reception interference and todramatically improve the SN ration, simply and inexpensively. Moreover,a user can omit the procedure of grounding the AM receiving apparatus100, which is normally preferred, so that it is possible tosignificantly improve the user's convenience.

(3) Second Study on Effect in Example

Next with reference to the aforementioned FIGS. 5, a second study isgiven to the effect in the example. FIGS. 5 are a graph (FIG, 5(a))quantitatively showing the effect of the example on the basis of gainlimited sensitivity (or maximum sensitivity) and a graph (FIG. 5( b))quantitatively showing the effect of the example on the basis of noiselimited sensitivity (or practical sensitivity).

As shown in FIG. 5( a), according to the research by the presentinventors, it is found out that the maximum sensitivity, which cannot bemeasured in the comparison example, can be measured in the AM receivingapparatus 100 in the example. As a result, it is found out that thenoise caused by the variation in the reference potential V0, is almostor completely cancelled, it is found out that the reception interferenceis prevented, and it is found out that the SN ratio is dramaticallyimproved, in the AM receiving apparatus 100. Here, the “gain limitedsensitivity (or maximum sensitivity)” in the example, denotes the levelof an input signal of the AM receiving apparatus, which is to output anoutput signal at a constant level, under the influence of the noise, inthe AM receiving apparatus. Specifically, the graph in FIG. 5( a),indicates such a level of the input signal that the level of the outputsignal is “−10(dB)”, if the output signal level is 0 dB when a referenceinput signal (74 dB μV/m) is inputted. Incidentally, the unit (dB μV/m)denotes a physical unit which indicates electric field intensity. Thelower gain limited sensitivity (or maximum sensitivity) means that themodulated signal can be listened to even at the lower input signallevel. In general, the lower maximum sensitivity is considered to have abetter reception capability.

However, if the apparatus is suppressed by the noise caused by thevariation in the reference potential, the noise is measured as theoutput signal, regardless of the magnitude of the input signal level.Thus, a value below the maximum sensitivity actually owned by thereceiver, is measured. And the maximum sensitivity cannot be alsomeasured in many cases, if the suppression level by the noise is high.

Specifically, as shown in “white circles” in FIG. 5( a), the gainlimited sensitivity in the comparison example, shows “NG (No Good:unmeasurable)” in the minimum reception frequency and the maximumreception frequency.

That is to say, the maximum sensitivity cannot be measured because ofthe suppression by the noise caused by the reference potential variationof the receiver from the switching power supply or the like provided inmeasured equipment. In contrast, the maximum sensitivity in the example,as shown in “black circles” in FIG. 5( a), shows values of “42” and “34”in the minimum reception frequency and the maximum reception frequency,respectively. It indicates that the noise caused by the switching powersupply or the like provided in the measured equipment, is canceled andit indicates that the maximum sensitivity can be measured. Incidentally,arrows in FIG. 5( a) indicate that the measurement can be changed frombeing incapable to being capable in the example, if the receptionfrequency has the minimum value or the maximum value. Moreover, in thereception frequency in FIG. 5( a) and in FIG. 5( b) described later, theminimum value indicates “531 (kHz)”, a value “A” indicates “603 (kHz)”,a value “B” indicates “999 (kHz)”, a value “C” indicates “1395 (kHz)”,and the maximum value indicates “1602 (kHz)”.

As shown in “black circles” in FIG. 5( b), according to the research bythe present inventors, it is found out that the level of the noiselimited sensitivity (or practical sensitivity) is substantially lowerthan that in the comparison example shown by “white circles”, in the AMreceiving apparatus 100 in the example. As a result, it is found outthat the noise caused by the variation in the reference potential V0, isalmost or completely cancelled, it is found out that the receptioninterference is prevented, and it is found out that the SN ratio isdramatically improved, in the AM receiving apparatus 100. Here, the“noise limited sensitivity (or practical sensitivity)” in the example,denotes the level of an input signal which is inputted to the AMreceiving apparatus when a constant SN ratio is obtained in the outputsignal under the influence of the noise, in the AM receiving apparatus.Specifically, the graph in FIG. 5( b) indicates a minimum input signallevel to obtain a SN ratio of 30 dB on the basis of the output signallevel when the reference input signal (74 dB μV/m) is inputted. Thelower noise limited sensitivity (or practical sensitivity) means thatthe modulated signal can be listened to even at the lower input signallevel without a problem in listening. In general, the lower practicalsensitivity is considered to have a better reception capability.

Specifically, as shown in the “black circles” in FIG. 5( b), it is foundout that the noise limited sensitivity (or practical sensitivity) in theexample, has values of “61”, “60”, “55”, “64”, and “53”, in the minimumreception frequency, a frequency “A”, a frequency “B”, a frequency “C”,and the maximum reception frequency, respectively, and that they aresubstantially lower than the noise limited sensitivity “83”, “65”, “65”,“62”, and “58”, respectively, in the comparison shown by “white circles”in FIG. 5( b). This indicates that the practical sensitivity is improvedby that the noise caused by the switching power supply or the likeprovided in the receiver, is eliminated, that the noise level withrespect to the output signal level is relatively reduced, and that theSN ratio is improved, in the example.

(4) Third Study on Effect in Example

Next with reference to the aforementioned FIGS. 6 and FIG. 7, a thirdstudy is given to the effect in the example. FIGS. 6 are a graph (FIG.6( a)) quantitatively showing the effect of the example on the basis ofattenuation and a graph (FIG. 6( b)) quantitatively showing the effectof the example on the basis of a SN ratio. FIG. 7 is a tablequantitatively showing the effect of the example on the basis of theattenuation and the SN ratio.

As shown in “black circles” in FIG. 6( a), according to the research bythe present inventors, it is found out that the level of the attenuationis more significantly reduced than the level of the attenuation in thecomparison example shown by “white circles”, in the AM receivingapparatus 100 in the example. As a result, it is found out that thenoise produced and caused by the variation in the reference potentialV0, is almost or completely cancelled, it is found out that thereception interference is prevented, and it is found out that the SNratio is dramatically improved, in the AM receiving apparatus 100. Here,the “attenuation” in the example denotes how much the output signallevel is attenuated if the input signal is minimal on the basis of theoutput signal level (0dB) when the reference input signal is inputted.Specifically, the graph in FIG. 6( a) indicates by a dB unit how muchthe output signal level is attenuated, if the input signal is “−∞”(dBμV/m) on the basis of the output signal level (0 dB) when “74”(dBμV/m) is inputted as the input signal. The higher attenuation meansthat there is less interference or that jamming by the noise is less. Ingeneral, the higher attenuation is considered to be better.

Specifically, as shown in the “black circles” in FIG. 6( a), it is foundout that the attenuation in the example has values of “−40” to “−26” inthe reception frequencies of “531 (Hz)” to “1602 (Hz)” and it is foundout that the attenuation in the example, is more significantly reducedin any of the reception frequencies than the attenuation of “−30” to“+6” in the comparison example shown in the “white circles” in FIG. 6(a).

More specifically, as shown in the table in FIG. 7, in the comparisonexample, there are “46” points of the sampled frequencies at which theattenuation is “−10 (dB)” to “−1 (dB)”. In contrast, in the embodiment,there are “0” points of the sampled frequencies at which the attenuationis “−10 (dB)” to “−1 (dB)”. Substantially in the same manner, in thecomparison example, there are “8” points of the sampled frequencies atwhich the attenuation is “0 (dB)” or more. In contrast, in theembodiment, there are “0” points of the sampled frequencies at which theattenuation is “0 (dB)” or more.

As described above, in the AM receiving apparatus 1.00 in the example,it is found out that the level of the attenuation is more significantlyreduced than in the comparison example. As a result, it is found outthat the noise produced and caused by the variation in the referencepotential V0 is almost or completely cancelled, it is found out that thereception interference is prevented, and it is found out that the SNratio is dramatically improved, in the AM receiving apparatus 100.

As shown in the “black circles” in FIG. 6( b), according to the researchby the present inventors, it is found out that the level of the SN ratiois higher than that the level of the SN ratio in the comparison exampleshown in “white circles” in FIG. 6( b), in the AM receiving apparatus100 in the example. As a result, it is found out that the noise causedby the variation in the reference potential V0 is almost or completelycancelled, it is found out that the reception interference is prevented,and it is found out that the SN ratio is dramatically improved, in theAM receiving apparatus 100. Here, the “SN ratio” in the example denotesa ratio in the output level between with and without the modulatedsignal by the dB unit, on the condition that a constant level of signalis inputted to the receiving apparatus. Specifically, the graph in FIG.6( b) indicates by the dB unit the ratio in the output level betweenwith the modulated signal (i.e. sine wave of 400 Hz) (in a modulationfactor of 30%) and without the modulated signal (in a modulation factorof 0%), on the condition that the reference input signal (74 dBμV/m) isinputted to the receiver. The higher SN ratio means that the noise levelis relatively small with respect to the modulated signal level and thata signal with less noise in listening can be listened to. In general,the higher SN ratio is considered to provide a better receiverperformance.

Specifically, as shown in the “black circles” in FIG. 6( b), it is foundout that the SN ratio in the example has values of “39” to “43” in thereception frequencies of “531 (Hz)” to “1602 (Hz)”, and that the SNratio in the example indicates a higher value in any of the receptionfrequencies than the SN ratio of “13” to “29” in the comparison exampleshown in the “white circles” in FIG. 6( b).

More specifically, as shown in the table in FIG. 7, in the comparisonexample (refer to columns of “conventional” in FIG. 7), there are “25”points of the sampled frequencies at which the SN ratio is in its “20s(dB)”. In contrast, in the embodiment, there are “0” points of thesampled frequencies at which the SN ratio is in its “20s (dB)”.

Substantially in the same manner, in the comparison example, there are“6” points of the sampled frequencies at which the SN ratio is less than“20 (dB)”. In contrast, in the embodiment, there are “0” points of thesampled frequencies at which the SN ratio is less than “20 (dB)”.

As described above, in the AM receiving apparatus 100 in the example, itis found out that the level of the SN ratio is higher than that in thecomparison example. As a result, it is found out that the noise causedby the variation in the reference potential V0, is almost or completelycancelled, it is found out that the reception interference is prevented,and it is found out that the SN ratio is dramatically improved, in theAM receiving apparatus 100.

In the aforementioned example, for example, the household or on-vehicleAM receiving apparatus, receiver, and transmitter are explained;however, the present invention can be applied to all the communicatingapparatuses using electromagnetic waves, such as video equipment andcommunication equipment for household use, or video equipment,communication equipment, and communication apparatus, for business use.

The present invention is not limited to the aforementioned example, butvarious changes may be made, if desired, without departing from theessence or spirit of the invention which can be read from the claims andthe entire specification. A communicating apparatus, which involves suchchanges, is also intended to be within the technical scope of thepresent invention.

INDUSTRIAL APPLICABILITY

The communicating apparatus of the present invention can be applied to,for example, a household or on-vehicle AM receiving apparatus, receiver,and transmitter. Moreover, the communicating apparatus of the presentinvention can be also applied to all the communicating apparatuses usingelectromagnetic waves, such as video equipment and communicationequipment for household use, or video equipment, communicationequipment, and communication apparatus, for business use.

1. A communicating apparatus comprising; a first antenna for receiving acarrier wave on which an information signal, which is a modulatedsignal, is superimposed; a ground terminal for bringing a referencepotential close to zero; a second antenna, (i) which is connected tosaid ground terminal and (ii) which has an electromagnetically reversepolarity of said first antenna; and a signal processing device forperforming signal processing on the received information signal.
 2. Thecommunicating apparatus according to claim 1, wherein (i) one end ofsaid second antenna is connected to said ground terminal and (ii) theother end of said second antenna is open or is terminated in animpedance of a predetermined amount substantially equivalent to the caseof being open.
 3. The communicating apparatus according to claim 1,wherein said first antenna and said second antenna areelectromagnetically integrally connected.
 4. The communicating apparatusaccording to claim 1, wherein said ground terminal is connected to (i) afirst reference terminal, which is the reference potential of saidsignal processing device, and (ii) all or a part of circuit elementsconnected to said first reference terminal.
 5. The communicatingapparatus according to claim 1, wherein said first antenna and saidsecond antenna are (i) electromagnetically integrally connected andphysically integrally connected, or (ii) electromagnetically integrallyconnected but not physically integrally connected.